The Research Animal Support Facility (RASF) has been a shared resource since the original Cancer Center Support Grant (CCSG) was awarded in 1975. The University of Texas M.D. Anderson Cancer Center has supported the RASF over these years, using institutional funds for the acquisition of major operational equipment and for remodeling and utility upgrades. The RASF has two distinct sites. One is within the perimeter of the Texas Medical Center, and the other is approximately 1 mile south of the Texas Medical Center at the Smith Research Building. Both animal facilities are accredited by the Association for Assessment and Accreditation of Laboratory Animal Core International, have an approved Animal Welfare Assurance Form (A3343-01), and are part of a research facility registered with the United States Department of Agriculture (74-R-065). The RASF is composed of three specific-pathogen-free (SPF) general rodent barriers, an SPF transgenic mouse barrier, a biohazard-use facility, conventional rodent housing, large-animal housing (for monkeys, dogs, pigs, and rabbits) and quarantine facilities. The RASF maintains approximately 37,000 animals daily; 98% are rodents, most of which are mice. The remaining 2% are monkeys, dogs, pigs, rabbits, guinea pigs, hamsters, and frogs. Also used are sea urchins and fruit flies. Animals are used to answer questions about how to diagnose, treat, and prevent cancer and to understand its causes. Investigators in all 13 research departments and in 24 of 29 clinical departments are supported by the RASF. In addition, clinical, surgical, diagnostic imaging,, and irradiation facilities and services are provided, as are diagnostic and pathology laboratory facilities and services. Specific SPF facilities for severe combined immuno-deficiency (SCID) mice use are also provided, and new, expanded SPF facilities for knockout and transgenic mice production and use are being developed, with occupancy expected in about April, 1998.